The fundamental structure of cell membranes is bilayers composed of phospholipids, and the vital function of the phospholipids in the membrane is to help keep it fluid and semi-permeable. Conventional glycerophospholipids have acyl chains attached to the sn-1 and sn-2 positions of the glycerol backbone via an ester bond. Ether lipids are a unique class of glycerophospholipids that have an alkyl chain attached to the sn-1 position by an ether bond (glycerol-ether lipids). In ether lipids, the alcohol group attached to the phosphate is generally choline or ethanolamine. Ether-linked phospholipids such as 1-alkyl-2-acyl-phosphatidylcholine and dialkylphosphatidylcholine are also found in the plasma and organelle membranes of mammalian species. Ether lipids form approximately 20% of the total phospholipid in mammals with different tissue distribution; brain, heart, spleen and white blood cells have the highest levels, while liver have a very little amount of ether lipids.
Studies on the formation and thermodynamic properties of ether-linked phospholipid bilayer membranes have indicated that in contrast to ester-linked phospholipid, the formation of the non-bilayer structure takes place spontaneously. This is attributed to the weaker interaction between polar headgroups in the ether-linked than that in the ester-linked phospholipids. It has also shown that the phase behavior of the ether-linked phospholipid bilayer membranes in ambient pressure is almost equivalent to that of the ester-linked phospholipid bilayer membranes under high temperatures and pressures, and the difference in the phase behavior decrease as the alkyl-chain length increases.
Due to distinctive properties of ether lipids, liposomes made from ether lipids exhibit very unique characteristics and performance: a) the ether bonds are more stable than ester linkages over a wide range of acidic or alkaline pH; b) stability properties of the liposomes is enhanced by bipolar lipids, and the saturated alkyl chains gives stability towards degradation in oxidative conditions; c) the unusual stereochemistry of the glycerol backbone enhance the resistance against the attacks by other organism phospholipases.
Phospholipase A2 (PLA2) cannot hydrolyze the ether lipid liposomes. Diether lipids do not go through hydrolysis due to having an ether bond instead of an acyl bond and therefore to do that, they are a suitable candidate for experiments that needs to be performed at a higher temperature for an extended period of time. For more information about hydrolysis and oxidation of phospholipids see here.
Saturated diether lipids can neither be hydrolyzed nor oxidized.
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转录的只是插入的片断，怎么会跟模板一样大呢，一般情况下应该比模板小多了。我都是跑电泳，严格来说应该跑变性的；嫌麻烦可以非变性，快速（防止RNA降解）十分钟即可；抛出来的带会有两条，上面大的是模板，下面一条比较亮的是RNA，那么你的转录就 成功了。
PCR第一个步骤如果没记错的话应该叫“变性”， PCR的话是不需要解旋酶的，直接利用DNA的高温变性特性，在高温下，使氢键断开，DNA双链恢复为单链。 （还有解旋酶好像是解除双螺旋的结构，是一种拓扑异构酶，对于氢键的打开没有贡献吧
首先，不否认它比大多数国产的试剂盒做得好，提取的纯度、方便度和量，都还很不错。
其次，它是日本的。so我觉得实验室用用天根的，就非常好了。拒绝日货，从实验室做起。
对于新手来说购买反转录试剂盒是比较理想的，买一个kit看看说明书操作就可以了。推荐两款kit TAKARA和HaiGene，这两款试剂盒都能对RNA样品中的gDNA有效去除，因此对RNA质量的要求不高。TAKARA的RR047A操作方便，反转录温度为37℃，对于大多数试验来讲是满足要求的。HaiGene的D0401操作要多一个步骤，但其反转录温度是55℃（耐高温的反转录酶），提高了反转录温度使得高GC含量、复杂模板、长mRNA的模板都能有效反转录，因此其反转录效率更高，更能够获得样本中基因的真实表达量。如果后续试验是RealTime PCR、ORF克隆、高GC含量、或者你的待研究基因结构复杂程度未知，还是选用耐高温的反转录酶更理想。对于反转录高手来说，直接购买反转录酶、再购买Rnase Inhibitor自己配制反转录体系就可以了。对于样本量大的课题组来讲，相对还是比较经济的。选择反转录酶时仅需要考虑是否需要耐高温的酶，来克服目的基因的复杂结构就可以了。PROMEGA、TAKARA、HaiGene、 TRANSGEN等品牌的反转录酶性价比还都是不错的。Life、NEB的也不错，不过性价比一般，不一一解释了。
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